replacing AHC globes/accumulators (1 Viewer)
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This is a great write-up with many helpful tips. I am replacing my accumulators on my 2002 LX and have the rears off (via the fan clutch wrench). The fronts are harder and I’ve soaked them the penetrating oil. My question is can I use an induction coil heater on the threads? I use it often on stuck nuts and bolts but am unsure about the globe. It resembles a bomb so I want to be sure I can heat it up without concern…
Thoughts??
Thanks in advance!
Thoughts??
Thanks in advance!
following this tread, Bought lx470 with 250000 miles, ride was very bouncy, AHC goes L to N to H with no issues although the marks at reservoir only moved 4 to 5 marks. Went ahead and changed 4 accumulators with aftermarket (maybe bad idea), followed instructions depressurizing the system, changed globes, and then bleeding each corner, AHC still goes from L to H with no problem but I'm still only moving 4 marks at the reservoir, and the ride got worse very rough and stiff ,I did notice when going from L to H at the reservoir when the pump stops working there's a visible "burp" in there, is this normal? or could I be getting air through there?
Could be the aftermarket ones. I purchased the factory ones and I now have a 7-10 change. Try getting them direct from Impex Japan. IMPEX JAPAN — online new genuine spare parts shop - https://en.impex-jp.com/ Price was about $200 per globe including shipping.
That burp following when the pump stops is normal
IndroCruise
SILVER Star
It looks like you are finding your way around the AHC and TEMS systems? Many of us have been there, done that, learnt the hard way, and lived to tell the tale!! Here is some information which may help, and also some suggested causes of the current issues ...
About 'globes' -- OEM or after-market?
Personally, I am too conservative to use anything other than the tried and proven OEM Toyota/Lexus 'globes' (Part Number Front: 49141-60010; Part Number Rear: 49151-60010) from IMPEX of Japan -- IMPEX JAPAN — online new genuine spare parts shop - https://en.impex-jp.com/ -- or from PARTSOUQ of UAE -- https://partsouq.com/ -- because I understand the OEM product, and I (and many other IH8MUD Members) have had good experiencces with these suppliers, and I know that I can expect OEM Toyota/Lexus 'globes' to be good for ~10 years, and some say much longer. The 'globes' are described in the LC100 and LX470 Factory Service Manuals as 'Gas Chambers' but elsewhere often are called 'spheres' or 'accumulators'.
The following pics and notes highlight OEM Toyota/Lexus 'globe' internal details including the 'globe' nitrogen pressure (the 'fill pressure') when the 'globe' was manufactured (not to be confused with AHC Fluid hydraulic pressures within the AHC system when the vehicle is in use). The quoted 'globe' nitrogen pressures are shown in the LC100 and LX470 Factory Service Manuals (FSM) -- see attached extract. These numbers are taken on trust because there is no way to measure these nitrogen pressures directly. Note that, as with any accumulator of this type, the membrane is never completely impermeable and the attachment of the membrane to the accumulator wall is never completely perfect. Given enough time (many years), some nitrogen pressure will be lost, even during shelf storage, and more quickly when the 'globe' is in use on the vehicle and the membrane is subject to continuous flexing and wear-and-tear.
Toyota/Lexus have been including these or similar 'globes' on progressive versions of LC100/LC200/LC300 and LX470/LX570/LX600 with Active Height Control (AHC) since 1998. The product specifications including dimensions, materials, fill presssures, and, reputation for reliability, longeivity and quality control are well-known, at leasr at a descriptive level.
It may be my obvious prejudice but I fear that aftermarket makers of alternative 'globes' provide very little (NIL?) technical information. Aftermarket products may be of lesser quality of manufacture and as a result may be less reliable and may be of shorter life.
That said, there is no reason not to try alternatives and other IH8MUD Members are doing so. A shorter life may be offset by lower cost and in that way give good value. Time and experience will tell.
For example, you may wish to follow @BullElk who certainly knows his way around the AHC and TEMS systems and has decided to try alternative 'globes' -- see his Post at this link:
Well I may have just committed one of the most blasphemous acts known to planet Mud. But because I am doing this for ALL mudders' benefit, so you don't have to, hopefully it is not worthy of a Mud Excommunication. 
The sin---- > I now have four Amazonian Chinese made globes in my '01 LX. ($379)
And as of today, with very aggressive big lug Prinx mudders, the ride is absolutely mint...mint I tell you. I mean perfect. Can't imagine it could be better even with stock Michelins.
Because of this sacrificial mudder research project, I will let you know when any or all globes fail.
The sin---- > I now have four Amazonian Chinese made globes in my '01 LX. ($379)
And as of today, with very aggressive big lug Prinx mudders, the ride is absolutely mint...mint I tell you. I mean perfect. Can't imagine it could be better even with stock Michelins.
Because of this sacrificial mudder research project, I will let you know when any or all globes fail.
So what is the "Graduation Test" (sometimes called the "HI/LO Test") all about?
The Test uses observation of the difference in 'graduations' of Fluid Level at the AHC Tank to measure the difference in AHC Fluid volume within the operating parts of the AHC system (shown by the stippling in the pic below) when the vehicle is at
- the "LO" height setting (least fluid within the system, much fluid is sent back to the AHC Tank), compared with,
- the "HI" height setting (much fluid within the system, least fluid in the AHC Tank.
As highlighted by @Jcreme, the Test must be done after both the Front AHC pressure and the Rear AHC pressure have been brought within the FSM specifications at "N" height, as set out in the attached FSM extract describing the Test. If this is not done, then spurious Test results will be caused by the different-to-FSM AHC pressures. The results then cannot be compared with the FSM values and the invalid test results are of no real use.
[Note: "N" height is the reference height for all AHC purposes, and from which the Suspension Electronic Control Unit (ECU) is programmed to set "LO" height and "HI" height when selected at the centre console switch].
If the "Graduation Test" a.k.a. "HI/LO Test" is done correctly over time (say annually) and in accord with the FSM-specifiied "standard conditions", then
- the AHC Fluid displaced from the fluid-filled 'Shock Absobers' (basically hydraulic struts) will be the same every time,
- the AHC Fluid displaced from the 'globes' will slowly decline over the years because the nitrogen will be lost slowly over the years and there will be progressively less nitrogen pressure to force AHC Fluid from the 'globes' back towards the AHC Tank
Late Edit in italics: A properly conducted test showing ~14 graduations indicates 'globes' which are in 'as new' condition. A properly conducted test showing ~7 graduations indicates that change-out of the set of four 'globes' is necessary for good damping performance and 'ride quality'. The decline will be progressive over time rather than instantaneous. Not all 'globes' will reach end-of-life simulaneously but, like other components in a set (for example brake pads), when one does reach end-of-life, it is likely that others are not far behind.
Personally, I would always replace the 'globes' as set so that I know that all is good and I also would replace the AHC Pump sub-assembly 48901-60010 @ USD183.79 Partsouq at the same time as part of the same big 'bleed' of the system and at the 20th Birthday I would consider replacing the whole AHC Pump Assesmbly 48910-60012 @ USD1,352.57 Partsouq -- but all of that is just my conservatism. Others prefer to spread the work out over a few years and may choose to replace 'globes' in pairs and deal with the AHC Pump as and when and if required -- nothing wrong with that -- for example:
Props to PADDO's AHC fluid replacement method! - https://forum.ih8mud.com/threads/props-to-paddos-ahc-fluid-replacement-method.925459/page-15#post-16048519
After suspect 'globes' have been removed, the so-called 'pencil test' can be used. This involves pushing on the 'button' on the membrane -- see pic above -- with a pencil or similar. If the membrane is soft and fluid is forced out of the 'globe', then it indicates that the membrane has ruptured, ALL nitrogen has been lost and fluid which has found its way into nitrogen space behind the membrane now emerges.
Apart from indicating when a 'globe' has completely ruptured and ALL nitrogen pressure is lost, the 'pencil test' is of no other use in determining 'globe' condition.
Consider for example a Front or Rear 'globe' which had nitrogen fill pressure of 2.26-2.84 Mpa (327-384 psi) at manufacture but has declined due to use and age to 1 Mpa (145 psi). Such a pressure will be way beyond the strength of most pencils - imagine pressing on a truck tyre at 145 psi (or even the ordinary inflation pressure of around 40 psi) -- there will be no discernible impression.
By way of illustation, in previous threads @suprarx7nut has related 'globe' nitrogen pressure to graduations in the "Graduation Test" a.k.a. "HI/LO Test" -- for example:
What is the cause of "AHC still goes from L to H with no problem but still only moving 4 marks at the reservoir, and the ride got worse, very rough and stiff"? -- as asked by @LEXMEX
Some possibilities and solutions may include:
1. Despite efforts to bleed, air remains in the AHC system. This prevents effective damping and causes poor ride quality and also prevents the "Graduation Test" a.k.a. "HI/LO Test" working properly because test effort lost in compressing unwanted air still in the system.
Assessment: Highly likely -- one of the most commom AHC problems reported on this Forum after major component changes -- much more bleeding required.
2. Front and/or Rear AHC pressures are very high, exceeding FSM specifications. This also prevents effective damping and causes poor ride quality. The "Graduation Test" a.k.a. "HI/LO Test" also is prevented from working properly because AHC pressures overwhelm the Test and in particular the ability of the nitrogen pressure behind the membrane to push AHC Fluid back towards the AHC Tank is reduced,
Assessment: Highly likely if there is no history of checking AHC Pressures and/or if vehicle is heavily loaded -- requires Techstream or other scanner to check AHC pressures then carry out front torsion bar adjustments and consider preloading or upgrading Rear coil springs to achieve AHC pressures within FSM-specified ranges.
3. Some or all of the new aftermarket 'globes' have been supplied with insufficient nitrogen 'fill pressure'.
This could happen as nothing is known about the specification, quality and consistency of the aftermarket 'globes'.
Assessment: Possible but seems much less likely to have multiple 'globe' failures than Causes (1) and (2) above -- in any case, best deal with the more likely causes above before spending more money,
4. Faulty Height Control Sensors causing incorrect vertical movements and positions during "Graduation Test" a.k.a. "HI/LO Test" (and at other times).
Height Control Sensors are 'wear items' in the AHC system and investigaton is important when taking over a LX470 or LC100 with AHC/TEMS, as guided by FSM and multiple IH8MUD threads concerning Height Control Sensors issues;
Assessment: Possible but seems less likely than Causes (1) and (2) above. As a preliminary, with vehicle on a level surface at "N" height, it is worthwhile to check hub-to fender heights at all four wheels, expecting around 19.50 to 19.75 inches at Front and around 20.50 inches at Rear. Then check whether vehicle responds with close-to-expected height changes at "LO" and "HI" as shown in the FSM table below:
5. Partial flow impediments at strainers in the fluid path inside the AHC Pump sub-assembly or within the strainer or valve assembly inside the Return Valve next to the AHC Pump sub-assembly.
Diagnosis of these situations requires more information than currently provided concerning the subject vehicle.
Assessment: Possible but seems less likely than the earlier Causes given above.
Last edited:
Jack90210
SILVER Star
Another white-paper-worthy response from @IndroCruise, thank you for that.It looks like you are finding your way around the AHC and TEMS systems? Many of us have been there, done that, learnt the hard way, and lived to tell the tale!! Here is some information which may help, and also some suggested causes of the current issues ...
About 'globes' -- OEM or after-market?
Personally, I am too conservative to use anything other than the tried and proven OEM Toyota/Lexus 'globes' (Part Number Front: 49141-60010; Part Number Rear: 49151-60010) from IMPEX of Japan -- IMPEX JAPAN — online new genuine spare parts shop - https://en.impex-jp.com/ -- or from PARTSOUQ of UAE -- https://partsouq.com/ -- because I understand the OEM product, and I (and many other IH8MUD Members) have had good experiencces with these suppliers, and I know that I can expect OEM Toyota/Lexus 'globes' to be good for ~10 years, and some say much longer. The 'globes' are described in the LC100 and LX470 Factory Service Manuals as 'Gas Chambers' but elsewhere often are called 'spheres' or 'accumulators'.
The following pics and notes highlight OEM Toyota/Lexus 'globe' internal details including the 'globe' nitrogen pressure (the 'fill pressure') when the 'globe' was manufactured (not to be confused with AHC Fluid hydraulic pressures within the AHC system when the vehicle is in use). The quoted 'globe' nitrogen pressures are shown in the LC100 and LX470 Factory Service Manuals (FSM) -- see attached extract. These numbers are taken on trust because there is no way to measure these nitrogen pressures directly. Note that, as with any accumulator of this type, the membrane is never completely impermeable and the attachment of the membrane to the accumulator wall is never completely perfect. Given enough time (many years), some nitrogen pressure will be lost, even during shelf storage, and more quickly when the 'globe' is in use on the vehicle and the membrane is subject to continuous flexing and wear-and-tear.
View attachment 3980333
Toyota/Lexus have been including these or similar 'globes' on progressive versions of LC100/LC200/LC300 and LX470/LX570/LX600 with Active Height Control (AHC) since 1998. The product specifications including dimensions, materials, fill presssures, and, reputation for reliability, longeivity and quality control are well-known, at leasr at a descriptive level.
It may be my obvious prejudice but I fear that aftermarket makers of alternative 'globes' provide very little (NIL?) technical information. Aftermarket products may be of lesser quality of manufacture and as a result may be less reliable and may be of shorter life.
That said, there is no reason not to try alternatives and other IH8MUD Members are doing so. A shorter life may be offset by lower cost and in that way give good value. Time and experience will tell.
For example, you may wish to follow @BullElk who certainly knows his way around the AHC and TEMS systems and has decided to try alternative 'globes' -- see his Post at this link:
Well I may have just committed one of the most blasphemous acts known to planet Mud. But because I am doing this for ALL mudders' benefit, so you don't have to, hopefully it is not worthy of a Mud Excommunication.
The sin---- > I now have four Amazonian Chinese made globes in my '01 LX. ($379)
And as of today, with very aggressive big lug Prinx mudders, the ride is absolutely mint...mint I tell you. I mean perfect. Can't imagine it could be better even with stock Michelins.
Because of this sacrificial mudder research project, I will let you know when any or all globes fail.
So what is the "Graduation Test" (sometimes called the "HI/LO Test") all about?
The Test uses observation of the difference in 'graduations' of Fluid Level at the AHC Tank to measure the difference in AHC Fluid volume within the operating parts of the AHC system (shown by the stippling in the pic below) when the vehicle is at
View attachment 3980334
- the "LO" height setting (least fluid within the system, much fluid is sent back to the AHC Tank), compared with,
- the "HI" height setting (much fluid within the system, least fluid in the AHC Tank.
As highlighted by @Jcreme, the Test must be done after both the Front AHC pressure and the Rear AHC pressure have been brought within the FSM specifications at "N" height, as set out in the attached FSM extract describing the Test. If this is not done, then spurious Test results will be caused by the different-to-FSM AHC pressures. The results then cannot be compared with the FSM values for the test and are of no real use.
[Note: "N" height is the reference height for all AHC purposes, and from which the Suspension Electronic Control Unit (ECU) is programmed to set "LO" height and "HI" height when selected at the centre console switch].
If the "Graduation Test" a.k.a. "HI/LO Test" is done correctly over time (say annually) and in accord with the FSM-specifiied "standard conditions", then
In this way, the correctly performed test gives an indication of the overall condition of the four 'globes' -- but it does not indicate the condition of any particular 'globe'.
- the AHC Fluid displaced from the fluid-filled 'Shock Absobers' (basically hydraulic struts) will be the same every time,
- the AHC Fluid displaced from the 'globes' will slowly decline over the years because the nitrogen will be lost slowly over the years and there will be progressively less nitrogen pressure to force AHC Fluid from the 'globes' back towards the AHC Tank
What is the cause of "AHC still goes from L to H with no problem but still only moving 4 marks at the reservoir, and the ride got worse, very rough and stiff"?
Some possibilities and solutions may include:
1. Despite efforts to bleed, air remains in the AHC system. This prevents effective damping and causes poor ride quality and also prevents the "Graduation Test" a.k.a. "HI/LO Test" working properly because test effort lost in compressing unwanted air still in the system.
Assessment: Highly likely -- one of the most commom AHC problems reported on this Forum after major component changes -- much more bleeding required.
2. Front and/or Rear AHC pressures are very high, exceeding FSM specifications. This also prevents effective damping and causes poor ride quality. The "Graduation Test" a.k.a. "HI/LO Test" also is prevented from working properly because AHC pressures overwhelm the Test and in particular the ability of the nitrogen pressure behind the membrane to push AHC Fluid back towards the AHC Tank is reduced,
Assessment: Highly likely if there is no history of checking AHC Pressures and/or if vehicle is heavily loaded -- requires Techstream or other scanner to check AHC pressures then carry out front torsion bar adjustments and consider preloading or upgrading Rear coil springs to achieve AHC pressures within FSM-specified ranges.
View attachment 3980370
3. Some or all of the new aftermarket 'globes' have been supplied with insufficient nitrogen 'fill pressure'.
This could happen as nothing is known about the specification, quality and consistency of the aftermarket 'globes'.
Assessment: Possible but seems much less likely to have multiple 'globe' failures than Causes (1) and (2) above -- in any case, best deal with the more likely causes above before spending more money,
4. Faulty Height Control Sensors causing incorrect vertical movements and positions during "Graduation Test" a.k.a. "HI/LO Test" (and at other times).
Height Control Sensors are 'wear items' in the AHC system and investigaton is important when taking over a LX470 or LC100 with AHC/TEMS, as guided by FSM and multiple IH8MUD threads concerning Height Control Sensors issues;
Assessment: Possible but seems less likely than Causes (1) and (2) above. As a preliminary, with vehicle on a level surface at "N" height, it is worthwhile to check hub-to fender heights at all four wheels, expecting around 19.50 to 19.75 inches at Front and around 20.50 inches at Rear. Then check whether vehicle responds with close-to-expected height changes at "LO" and "HI" as shown in the FSM table below:
View attachment 3980345
5. Partial flow impediments at strainers in the fluid path inside the AHC Pump sub-assembly or within the strainer or valve assembly inside the Return Valve next to the AHC Pump sub-assembly.
Diagnosis of these situations requires more information than currently provided concerning the subject vehicle.
Assessment: Possible but seems less likely than the earlier Causes given above.
